What's the largest part of the heart

I’m doing some practice exam questions for biology, and i’m not sure how to do these 3 parts to the question.

Of seawater increases with decrease in the temperature. therefore, the cold water sinks to the deeper layers at the bottom

How are the testes and ovaries similar? a. both produce sex cells. b. both connect internal reproductive organs to the exterior. c. both transport sex cells from their site of production. d. both store mature sex cells.